Yes that seems to be the correct understanding. The thief probably stayed at the place and made a copy of the key. Afterwards they rented it out on abnb.
Not sure if he is actually a thief. He claims to be a friend of the deadbeat tenant who actually rents here. That does sound like a likely story. I don't want to get involved more than I need to, I'm on vacation anyway. Makes for one heck of a story back home though.